Metal coating method and apparatus



METAL COATING METHOD AND APPARATUS Filed Dec. '7, 1955 (sheets-sheet 1INVENTORS Ralph W.H0d i| JoredLHolt ATTORNEYS Sept. 20, 1955 R. w. HODILET AL 2,713,474

METAL COATING METHOD AND APPARATUS Filed Dec. '7, 1953 4 Sheets-Sheet 2BY "(77? I 1/ I q f? i "11 J0 red LHoh f;

ATTORNEYS p 20, 1955 R. w. HODIL ET AL 2,718,474

METAL COATING METHOD AND APPARATUS Filed Dec. '7, 1955 4 Sheets-Sheet 3I, 5 Ralph W.Hodil f. JaredLHoh BY Mvh ATTORNEYS R. W. HODIL ET AL METALCOATING METHOD AND APPARATUS 4 Sheets-Sheet 4 liFFd INVENTORS m WL d 6mr 00 d BY $777M ATTORNEYS Sept. 20, 1955 Filed Dec. 7, 1955 UnitedStates Patent ()fiice 2,718,474 Patented Sept. 20, 1955 METAL COATINGMETHOD AND APPARATUS Ralph W, Hodil, Pittsburgh, and Jared L. Holt,Butler, Pa.

Application December 7, 1953, Serial No. 396,519

6 Claims, (Cl. 117-51) This invention relates to metal coating methodand apparatus, and more particularly to a method and apparatus forcoating tubular members, such as metal pipes.

The non-electrolytic coating of metal objects, such as iron pipes, witha galvanizing coating of zinc is a process which often involves manytroublesome problems. The metal which is' to be coated must be raised tothe proper galvanizing temperature which is in the range 850875 E. Inorder to offset the lowering in temperature due to the entry of the coldpipe or other object to be coated, the metal has to be heated to ahigher temperature. However, if the zinc bath itself is heated to thehigher temperature by the application of heat to the tank or kettlecontaining the zinc, a reaction occurs between the iron oi the kettleand the zinc bath which results in rapid deterioration of the kettle,thereby greatly shortening the life of the kettle and increasingformation of dross.

One method which has been proposed for overcoming the ditiiculty justmentioned is to preheat the metal pipe or other metal object to theproper galvanizing temperature by passing the object to be coatedthrough a preheating bath of another metal, such as lead, which servesonly as a preheating medium. This preheating step generally involvesfloating the zinc coating material on the lead preheating bath, both thelead and zinc being contained in the same tank or kettle. The metalobject, such as the iron pipe, is drawn upwardly through the leadpreheating bath and then through the upper floating layer of zinc.

The method just described has several serious objections. For example, adross composed of a zinciron compound forms when the zinc coating isapplied over an iron surface, and drops to the bottom of the floatinglayer of zinc, but remains above the preheating bath oflead. As aresult, the metal pipe or other object being coated is drawn through thelayer of dross before passing through the zinc bath. This results inimperfect coatings and poor appearance of the object being coated.Furthermore,-in this kind of lead-zinc process, the lead bath is inconstant contact with the supply of zinc and picks up and holds aboutone per cent of zinc. This amount of zinc is sufiicient to cause thelead to have some aflinity for the iron or steel member being coated,with the result that the speed of passage of the work through the bathis limited due to the fact that globules of lead adhere to the work,damaging the coating and ruining its appearance. Also, due to the factthat the hot lead bath contains a certain percentage of zinc from itsdirect contact with the zinc layer, the machinery for moving thematerial to be coated, and the tank or kettle are chemically attacked tosome degree by reaction with the zinc, although this reaction occurs toa lesser degree than if the bath were all zinc.

Still another problem which occurs in the method just described is thedanger of entrapment of dross in the interior of the pipe, requiringblowing at high pressure to make sure that there is no plugging of thepipe by such dross.

Another problem which is often encountered in gale vanizing processes inaccordance with the prior art is the oxidation which occurs if the zinccoating is applied in an open atmosphere. An outer layer of oxidizedzinc forms in the zinc bath and has to be skimmed off, resulting inconsiderable waste. In fact, a substantial percentage of the molten zincused in accordance with prior methods of zinc coating is lost insofar asthe galvanizing process is concerned, due to reaction either with theatmosphere or with the kettle or tank in which the galvanizing processtakes place.

Accordingly, it is an object of this invention to provide an apparatusand method for applying a galvanizing coating of zinc to metalobjects'in accordance-with which the galvanizing coating material isheated to not in excess of the galvanizing temperature, and wherein theobject to be coated is heated in a separate preheating bath.

it is another object of this invention to provide a method and apparatusfor applying a coating of zinc to an iron or steel member which greatlyreduces chemical reaction between the zinc coating material and itscontaining kettle, thereby greatly prolonging the life of the kettle;

It is another object of this invention to provide a method and apparatusfor applying a coating of zinc to an iron or steel member in which apurer coating of zinc is obtained than is possible using methods andapparatus of the prior art.

Still anotherobject of this invention is to provide an apparatus andmethod for applying a zinc galvanizing coating to a metal object, suchas a tubular pipe, in which the zinc galvanizing bath is maintained outof contact with the preheating bath, such as a lead preheating bath.

Still another object of this invention is to provide an apparatus andmethod for applying a galvanizing coating to a metal object in which thegalvanizing process occurs in an atmosphere which is inert to thegalvanizing material, Such as zinc.

Still another object of the invention is to provide a simple anduncomplicated galvanizing apparatus which expeditiously and efljcientlymoves the object to be galvanized, such as an iron or steel pipe,successively through a flu bath. a prehe a h. and a lvan zing a h n th rbj t t e ti n is't P v e n pparatus and method for coating metal pipeswith zinc in, accordance with which production of dross is greatly e dan he p u in Qt P p by dross is su a a ly eliminated.

A still further object of the invention is to provide an apparatus andmethod for galvanizing metal pipes which permits a much higher outputthan is possible using the apparatus and methods of the prior art.

In achievement of these objectives, this invention provides an apparatusand method in which metal pipes to, be galvanized are carried by aconveyor system first, through a flux or acid bath to remove oxidation,then through a preheating bath of hot lead to heat the pipes to thegalvanizing temperature, and then through a' gal. vanizing bath of zinc.'Each of the baths is contained in a separate tank, and each tank isprovided with a separate rotary conveyor which carries the pipes in acircular path first downwardly and then upwardly through the given bath.The successive tanks are connected by inclined guide-ways or ramps downwhich the pipes roll to be picked up by the conveyor of the succeedingbath. The galvanizing bath tank, the preheating bath tank and part ofthe flux bath tankare enclosed in a substantially. airtight structurewhich is filled above the levels of the respective baths. with anatmosphere of a gas inert to the galvanizing material, such as zinc. Thepipes to be coated enter and leave the various baths at an angleinclined to the horizontal so that the liquids drain from the interiorof the pipes upon leaving the baths. Furthermore, the structure is soarranged that the air inside the pipes to be coated is purged as itenters the flux bath and is filled with the inert gas as it emerges fromthe flux bath. 'This prevents any air contained in the interior of thepipes from being carried into the preheating and galvanizing tanks insuch manner as to contaminate the inert atmosphere in those tanks.

'Other objects and advantages of the present invention will become moreapparent from the following detailed description taken in conjunctionwith the attached drawings in which:

Fig. 1 is a top plan view of a galvanizing apparatus in accordance withthe invention;

Fig. 2 is a view in section along line 2-2 of Fig. 1;

Fig. 3 is a view in section along line 33 of Fig. 4 showing details ofthe sealing doors between the flux bath and the preheating lead bath;

Fig. 4 is a view in section along line 44 of Fig. 1; Fig. 5 is anenlarged detail view, partially cut away, showing the support andlifting arrangement for the box girders which, in turn, support theconveying mechanism. within the respective baths;

Fig. 6 is an enlarged sectional detail view showing the supporting andsealing arrangement for the removable covers of the galvanizingapparatus; and

Fig. 7 is an enlarged detail view of one of the tanks, showing themanner in which the pipe conveying mechanisms and cover are lifted;

Referring now to the drawings, the galvanizing apparatus comprises threetanks 10, 12 and 14 which extend parallel to each other, but in spacedrelation, tank being supported by a suitable concrete foundation 16, asshown, while the other tanks are supported on brick work 16a. Tank 10serves as a receptacle for a bath of an acid, such as muriatic acid,which removes all traces of dirt and oxide on the surfaces of the pipesto be galvanized, to thereby provide the pipes with a surface to whichthe galvanizing solution will readily adhere. Tank 12 serves as areceptacle for a bath of hot lead, which serves as a preheating mediumto raise the pipes to the galvanizing temperature of 850875 F. Tank 14serves as a receptacle for the zinc bath which provides the galvanizingcoating for the pipes.

A heating chamber 18 surrounds the side walls of the lead bath tank 12,and includes openings 20 through which a gas fired heating means extendson either side of the side walls of the tank 12 in order to raise thetemperature of the lead bath to the required range. Similarly, a heatingchamber 22 extends longitudinally on either side of the tank 14 whichcontains the zinc bath, and electrical heating elements 24 serve to heatthe chamber 22 and the contents of the tank 14 to the desiredtemperature range.

The pipes to be coated are delivered to the flux bath tank 10 by meansof a conveyor 26, as will best be seen in Fig. 4. The pipes areautomatically delivered to the conveyor 26 from a water tank in whichthey are placed after a pickling process. pleted the galvanizingprocess, they are delivered to a water bath 28, shown at the left ofFig. 4, by means of an inclined guideway 30, the pipes then beingcarried out of the water bath by an upwardly moving conveyor 32.

To serve as a support for the enclosing cover which is to be laterdescribed, and also as a support for the con veying mechanism withineach tank, box girders 34, 36 and 38 extend above each of the respectivetanks 10, 12 and 14. Each of the box girders 34, 36, 38 is supported atits opposite ends by the oppositely disposed cantilever beam members 40and 42 (Figs. 1 and 2). The beams 40 and 42 in turn are supported attheir outer ends by the pillars or walls 44.

As will best be seen in Figs. 2 and 5, the box girders 34, 36, 38 areprovided at each end with a stepped portion 50, which is supported by amating stepped portion 52 of the respective beams 40 and 42.

In order to permit detachable engagement of the After the pipes have combox girders with the supporting beams, each end of the girders 34, 36and 38 is provided with an upstanding bracket member 53 having rigidlyattached thereto and extending therefrom a pair of apertured guideelements 54 which engage the vertical post 56, see Fig. 5, extendingfrom each of the respective beam members 40 and 42.

Each box girder 34, 36, 38 serves as a support for the conveyingmechanism within one of the respective tanks 10, 12, 14. Within each ofthe tanks, a plurality of large serrated disk members 60, see Fig. 4,are rigidly attached to a rotatable shaft 62 which extendslongitudinally within each of the respective tanks. The disks are spacedalong the shaft 62, as can best be seen in the view of Fig. 2. The shaft62 in any one tank is supported by a plurality of spaced bearingbrackets 64 which extend downwardly from the respective one of the beams34, 36, 38 which extends above the given tank. Cooperating with each ofthe serrated disks 60 is a guide plate 66 which is supported by the baseof the tank and which has an arcuate cut-away portion of just slightlysmaller peripheral extent than the periphery defined by the teeth of therespective disks 6%). The guide plate 66 serves to retain the outersurface of the pipes as they are fed through the bath by the rotatingserrated disk 60. Cooperating with the guide plates for this purpose arethe auxiliary plates 66a located adjacent to the tops of the disks 60,on the rising sides thereof, as shown in Fig. 4.

As will best be seen in Fig. 2, each of the respective guide plates 66is ofiset longitudinally of the tank a short distance from the plane ofthe respective disk member 60 with which it cooperates to permit aslight overlapping between the outer periphery of the disk 60 and theinner periphery of the guide plate 66.

Mounted above and adjacent the serrated disks 60 in each of therespective tanks are a plurality of star wheels 68. In the embodimentshown, a star wheel is positioned adjacent every other disk 69, see Fig.2. The star wheels 68 are mounted on a shaft 70 which, in turn, issupported by the same bearing brackets 64 which support the shaft 62.The star wheels 68 serve to pick up the pipes from the disks 60 afterthe pipes have completed their rotation through the given bath.

In order that the pipes which are carried by the conveyor system enterand leave the various baths at an inclination to the horizontal in orderto permit drainage of the liquid from the pipes as they emerge from thebath, and also to permit purging of air from the pipes in the flux bathof tank 18*, the shafts 62 and 70 which support the serrated disks 60and star wheels 68 are so mounted as to be inclined at a predeterminedangle with respect to the horizontal, as can best be seen in the view ofFig. 2. Thus, for example, the shafts 62 and 70 may be inclined from thehorizontal by 4 inch per foot of length.

The shafts 62 and 70 in each of the respective tanks is driven by avertical drive shaft 72 having worm threads 74 which cooperate with wormwheels '76 on the respective shafts 62 and '70. At its upper end, eachof the respective vertical shafts 72 is provided with one of a pair ofmating offset bevel gears 77 which are driven from a horizontallyextending auxiliary drive shaft 78 through a suitable clutching device80. Each of the auxiliary drive shafts 78 is connected through a gearingand clutch arrangement generally indicated at 82 to a main drive shaft84 which is driven by a suitable power source generally indicated at 86.

An important feature of the invention is the provision of an air tightenclosure means over the galvanizing tank 14, the lead bath tank 12, andpart of the flux tank 10. This enclosure means serves to insure that thegalvanizing process is conducted in an inert atmosphere which preventsharmful oxidation of the zinc galvanizing material.

The enclosure means over the tanks includes, as shown in Fig. 4, thecover sections 99, 92., 93 and 94, the cover portions 96 and 98 attachedto the upper surfaces of the respective box girders 36 and 38, thelongitudinally extending walls 184 and 186, the laterally extendingwalls 108, and the sealing Walls or bafiles 109 and 11 which dependdownwardly from the respective box girders 34 and 36 into tanks and 12respectively. The cover sections 90, 98, 92, 96, 93 and 94 all lie inthe same horizontal plane and together form the top cover for thegalvanizing apparatus. The cover sections are removable and are eachprovided with a sealing means comprising downwardly extending fins orvanes 10% which seat in liquid recesses 102, see Figs. 4 and 7, attachedto the sides of the box girders and of the various walls which the coversections engage, to provide an air tight enclosure. Thus, the end wall184, shown at the left of Fig. 4, the intermediate wall 106 between thetanks 10 and 12, and the transversely extending walls 108 (Fig. 6), aswell as each of the box girders 34, 36, 38 are provided with the liquidfilled recesses 102 which engage the downwardly depending vanes 160 ofthe various cover sections to provide an air tight seal.

The enclosure is further sealed by flexible sealing means 107 (Fig. 6)which connect the underneath edges of the transversely extending walls108 to their supporting foundation- 115. When the cover sections are inplace, the atmosphere above the zinc bath in tank 14, above the hot leadbath in tank 12, and above part of the flux bath in tank 10 issubstantially enclosed and sealed from the exterior atmosphere. Thelongitudinally extending wall portion 111 which depends downwardly frombox girder 36 to slightly below the level of the bath in tank 12 servesas a means which tends to isolate the atmosphere to the left of the Wall111, With respect to the view shown in Fig. 4, from the atmosphere tothe right of the wall 111. In a similar manner, the sealing wall 109which depends downwardly from the box girder 34 tends to isolate theatmosphere to the left of wall 109 from that to the right of wall 169,with respect to the view shown in Fig. 4. The entire enclosed space fromend wall 104 to sealing wall 109 is filled with a protective atmospherewhich is inert to the zinc coating material and may be, for example, amixture which is 96 /2 percent nitrogen (N2) and 3 /2 percent hydrogen(H2).

It will be noted that while the interiors of the galvanizing tank 14 andof the lead bath tank 12 are completely covered by means of the covermembers 90, 96, 92,. 98, and 93, the flux bath tank 10 into which thepipes are first introduced is only partially covered by the cover member94. The box girder 34 is positioned laterally inwardly a short distancefrom the outer wall of the tank 10 and the wall or baffle member 1439extends vertically downwardly from the underneath surface of the boxgirder 34 to a distance somewhat below the level normally maintained bythe liquid in tank 10. The wall or baffie member 109 is suitablyapertured to permit passage therethrough of the bearing bracket 64 whichsupports the shafts 62 and 70 and is also apertured or slit to permitrotation therethrough of the serrated disk members as they move throughthe flux bath in tank 10, the slit formation closely cooperating withthe disk member to prevent loss of the protective atmosphere orcontamination thereof.

An inclined guide-way or ramp 110 extends between the discharge end ofthe tank 10 and the inlet end of the tank 12. The guide-way is inclinedin such manner that the pipes delivered to the upper end of the guidewaywithin the chamber 10 roll by gravity to the lower end of the guide-way,where they pass to downwardly inclined guide-way 112 in tank 14, wherethey are picked up by the disks 60 within the tank 12. A series ofnormally closed hinged doors 114 are positioned at spaced apartintervals along the downwardly inclined guide-way 110. As each piperolls down guide-way 110, it forces Pen the successive doors 114 whichreturn to their normally closed position as soon as the pipe has passedthrough the door. In the embodiment shown, five doors 114 are provided.These doors serve as seals which tend to prevent loss of largequantities of the inert or protective atmosphere from the tanks 12 and14, and further tend to isolate the atmosphere or tanks 14 and 12 fromthat of tank 10.

The lead bath tank 12 and the galvanizing tank or kettle 14 areconnected by a ramp or inclined guideway 116 so that pipes which aredischarged from tank 12 roll downwardly due to the force of gravity andare delivered by guide-way 118 into the tank 14 where they are picked upby the rotating serrated disks in tank 14.

An inclined guide-way 118 permits pipes which are discharged from thetank 14 to pass downwardly to the discharge end of the apparatus Wherethey pass through a normally closed hinged door 120 which is forced openby the passage of the pipe but which returns to its normally closedposition after the pipe has passed through.

To facilitate removal of the cover members, lifting lugs 122 areprovided on each of the respective cover sections 90, 92, 93 and 94.

The box girders 96 and 98 are each provided with a lifting lug 124 whichis inclined at an angle away from the vertical in order that the pointof attachment of the lifting hook will be over the center of gravity ofthe rig attached to the respective box girders, which includes the disks60, the star wheels 68 and their supporting shafts.

As most clearly illustrated in Fig. 7, when it is desired to remove thecover sections for any reason, such as to periodically remove the drosswhich settles at the bottom of the galvanizing kettle or tank 14 due tothe reaction of the zinc with the iron pipes or other metal object beingcoated, the covers may be lifted by attaching a hoist hook 125 to thelifting lugs 122. After the cover sections have been removed, the boxgirders may be removed by attaching the hoist hook to the lifting lugs124, thereby causing the conveying mechanism, including the disks 60,the star wheels 68., and their supporting shafts to be raised out of therespective tank in which they are located.

In the operation of the apparatus, when it is desired to galvanize metalpipes, the lead bath in tank 12 is heated to the required temperaturerange of 850875 F. and the zinc plating solution is heated to itsrequired temperature. The disks 60 in each of the respective tanks andthe star wheels 68 are caused to rotate by energizing the prime mover86, the main drive shaft 84, the auxiliary drive shafts 78 and thevertical drive shafts 72. This causes rotation of the shafts 62 and 70which respectively carry the serrated disks 60 and the star wheels 68.The pipes which are to be metal plated are then delivered by conveyor 26down the inclined guide-way 27 into the flux bath of tank 10 where theyare picked up by the teeth of the plurality of serrated disks 60. Thepipe P is supported at an inclination to the horizontal due to theinclination of the shaft 62.

As the disks 60 rotate, one end of the pipe passes into the fluxsolution first and causes any-air in the interior of the pipe to bepurged from the pipe as the pipe passes down into the solution. The pipeis then rotated through the solution, being guided by the guide plates66. After completing its circular path of rotation in the tank 10, andhaving had dirt and oxidation removed from its outer surface, the pipeis picked up by the star wheels 68 in tank 10 and delivered to the rampor inclined guide-way 110;. The atmosphere above the portion of tank 10where the pipes emerge from the flux or muriatic acid bath is asubstantially inert atmosphere, since the interior of tank It) is to alarge extent sealed by the sealing wall or bafiie 108. Hence, the pipeshave been purged of air as they enter the muriatic acid bath and arefilled with the inert atmosphere as they emerge from the bath at thetime of their delivery to the ramp 110. The pipe rolls down the ramp 110and passes through each of the successive sealing doors 114, each door114 closing as the pipe passes by it. This prevents excessive escape ofthe inert atmosphere from tank 12.

At the end of the guide-way 110, the pipe is picked up by the guideway112 and delivered to the rotating serrated disks 60 in tank 12. Thesedisks carry the pipe through the bath of hot lead which raises thetemperature of the pipe to the temperature of the lead bath, which isthe same as the temperature required for the metal coating step. Afterhaving completed its rotary path of motion in tank 12, the pipe ispicked up by the star wheels 68 and delivered to the ramp or inclinedguide-way 116. The pipe rolls down guide-way 116 due to the force ofgravity and passes down inclined guide-way 118 in tank 14, where it ispicked up by the rotating disks 60 of that tank. The disks 60 carry thepipe through the zinc bath and the coating of zinc is deposited on theouter and inner surfaces of the pipe. After completing its path ofmotion through the zinc bath, the pipe is picked up by the star wheels68 and delivered to the inclined ramp or guide-way 118, rolls downguide-way 118 due to the force of gravity and passes out through thenormally closed door 120 which is opened due to the force of the rollingpipe striking it. The door 120 closes as soon as the pipe has passedthrough. After passing through the door 120, the pipe rolls down theinclined guide-way into the water bath 28 and is carried out of thewater bath by the conveyor 32.

It can be seen from the foregoing that there is provided in accordancewith this invention an improved method and apparatus for applying metalcoatings, such as zinc coatings, to metal pipes. The invention providesa method in accordance with which the metal coating process occurs in anatmosphere which is inert to the zinc, thereby preventing oxidation ofthe zinc. Furthermore, the invention provides an apparatus which permitsthe pipes to be preheated to the required galvanizing temperature in alead bath which is entirely out of contact with the zinc bath, therebyavoiding injurious chemical reactions which occur when the zinc bathitself is heated to the galvanizing temperature. The apparatus of theinvention permits pipes to be efficiently conveyed through the fluxbath, the lead preheating bath and the zinc bath in succession,resulting in much faster production of metal plated pipes than ispossible using the methods and apparatus heretofore known. Furthermore,the amount of dross formed in the Zinc plating tank is substantiallyreduced as compared to the amount of dross normally obtained. As aresult, a much purer and more uniform zinc coating is obtained than ispossible using conventional apparatus and methods, and plugging of pipesby dross is substantially eliminated.

What is claimed is:

1. Apparatus for the treatment and coating of tubular elementscomprising first tank means for containing flux solution, second tankmeans for containing molten metal for preheating the tubular elements,and third tank means for containing the molten coating metal, conveyormeans for conveying the tubular elements through each of said tankmeans, and protective enclosure means for said second and third tankmeans and at least part of said first tank means for enclosing above thecontents of each tank means a protective atmosphere, said conveyor meansincluding fixed plates each having a cutaway portion providing an edgeover which the tubular elements are moved, rotatably mounted cooperativemembers provided with tubular element-receiving surface portionspredeterminately disposed relative to said fixed plates so as tospacedly hold said tubular elements, said cooperative members havingdriving means for moving said elementreceiving surface portions relativeto said plates, said fixed plates being disposed in successively steppedrelation and the cooperative members being mounted on an inclined axisso as to convey the tubular elements in slightly inclined relationship,and said protective enclosure means including a depending sealing wallprojecting into the first tank means below the level of its contents andin spaced relation to one end wall thereof so that upon entry of thetubular elements into the contents of the first tank means between suchone end wall and the sealing wall the air is purged from the tubularelements and upon exit from said first tank means the tubular elementsfill with protective atmosphere for passage into the second tank means.

2. Apparatus for the treatment and coating of tubular elementscomprising first tank means for containing flux solution, second tankmeans for containing molten metal for preheating the tubular elements,and third tank means for containing the molten coating metal, conveyormeans for conveying the tubular elements through each of said tankmeans, and protective enclosure means for said second and third tankmeans and at least part of said first tank means for enclosing above thecontents of each tank means a protective atmosphere, said conveyor meansincluding fixed plates each having a cutaway portion providing an edgeover which the tubular elements are moved, rotatably mounted cooperativemembers provided with tubular element-receiving surface portionspredeterminately disposed relative to said fixed plates so as tospaccdiy hold said tubular elements, said cooperative members havingdriving means for moving said elementreceiving surface portions relativeto said plates, said fixed plates being disposed in successively steppedrelation and the cooperative members being mounted on an inclined axisso as to convey the tubular elements in slightly inclined relationship,and said protective enclosure means including a depending sealing wallprojecting into the first tank means below the level of its contents andin spaced relation to one end wall thereof so that upon entry of thetubular elements into the contents of the first tank means between suchone end wall and the sealing wall the air is purged from the tubularelements and upon exit from said first tank means the tubular elementsfill with protective atmosphere for passage into the second tank means,said protective enclosure means having plural normally closed doorsbetween said first and second tank means through which doors the tubularelements successively pass.

3. Apparatus for the treatment and coating of tubular elementscomprising first tank means for containing flux solution, second tankmeans for containing molten metal for preheating the tubular elements,third tank means for containing the molten coating metal, conveyor meansfor conveying the tubular elements through each of said tank means, andremovable protective enclosure means for at least said second and thirdtank means for containing a protective atmosphere, said conveyor meansincluding first ."neans disposed within each of said tank means forconveying the tubular elements through the contents of the respectivetanks, and second means for consecutively transferring the tubularelements between the tank means, and common means supporting the firstand second means from said removable protective enclosure means.

4. Apparatus for the treatment and coating of tubular elementscomprising first tank means for containing flux solution, second tankmeans for containing molten metal for preheating the tubular elements,and third tank means for containing the molten coating metal, conveyormeans for conveying the tubular elements through each of said tankmeans, said conveyor means including a plurality of plates fixed Withineach of said tank means and each having a cut-away portion providing anedge over which the tubular elements are moved, a serrated discrotatably mounted adjacent each of said fixed plates and all of theserrated discs within each tank means being connected for commonrotation, a plurality of star wheels mounted for common rotation withineach tank means above said serrated discs, and inclined elementsdisposed between the tank means for receiving tubular elementsdischarged from the star wheels, protective enclosure means for at leastthe second and third tank means for containing a protective atmosphere,said protective enclosure means including cover sections removablysealingly associated with the several tank means, means for individuallyremoving said cover sections, and means connecting certain of said coversections over respective tank means with said serrated discs and saidstar wheels whereby the serrated discs and star wheels are removablewith such cover sections.

5. The method of applying a galvanizing coating of zinc on ferroustubular elements which comprises passing the tubular elements through aflux solution, passing the tubular elements through a separatepreheating bath approximately in the galvanizing temperature range andcontaining a molten metal having substantially no afiinity for theferrous tubular elements, and passing the tubular elements through aseparate body of molten galvanizing metal the temperature of which iswithin the galvanizing temperature range.

6. The method of applying a galvanizing coating of zinc on ferroustubular elements which comprises passing the tubular elements through aflux solution, purging the tubular elements of the air containedtherein, filling the tubular elements with protective atmosphere,passing the tubular elements through a separate preheated bath 10approximately in the galvanizing temperature range which bath consistsof a molten metal having substantially no affinity for the ferroustubular elements and which is protectively covered with a protectiveatmosphere, and passing the tubular elements through a protectivelycovered, separate body of molten galvanizing metal the temperature ofwhich is within the galvanizing temperature range.

References Cited in the file of this patent UNITED STATES PATENTS2,111,826 Waltman et al. Mar. 22, 1938 2,135,387 Dellgren Nov. 1, 19382,159,297 Shover May 23, 1939 2,166,250 Herman July 18, 1939 2,197,622Sendzimir Apr. 16, 1940 2,276,232 Gilbert Mar. 10, 1942 2,405,221 MannAug. 6, 1946 FOREIGN PATENTS Germany Apr. 15, 1939

1. APPARATUS FOR THE TREATMENT AND COATING OF TUBULAR ELEMENTSCOMPRISING FIRST TANK MEANS FOR CONTAINING FLUX SOLUTION, SECOND TANKMEANS FOR CONTAINING MOLTEN METAL FOR PREHEATING THE TUBULAR ELEMENTS,AND THIRD TANK MEANS FOR CONTAINING THE MOLTEN COATING METAL, CONVEYORMEANS FOR CONVEYING THE TUBULAR ELEMENTS THROUGH EACH SAID TANK MEANS,AND PROTECTIVE ENCLOSURE MEANS FOR SAID SECOND AND THIRD TANK MEANS ANDAT LEAST PART OF SAID FIRST TANK MEANS FOR ENCLOSING ABOVE THE CONTENTSOF EACH TANK MEANS A PROTECTIVE ATMOSPHERE, SAID CONVEYOR MEANSINCLUDING FIXED PLATES EACH HAVING A CUTAWAY PORTION PROVIDING AN EDGEOVER WHICH THE TUBULAR ELEMENTS ARE MOVED, ROTATABLY MOUNTED COOPERATIVEMEMBERS PROVIDED WITH TUBULAR ELEMENT-RECEIVING SURFCE PORTIONSPREDETERMINATELY DISPOSED RELATIVE TO SAID FIXED PLATES SO AS TOSPECEDLY HOLD SAID TUBULAR ELEMENTS, SAID COOPERATIVE MEMBERS HAVINGDRIVING MEANS FOR MOVING SAID ELEMENTRECEIVING SURFACE PORTIONS RELATIVETO SAID PLATES, SAID FIXED PLATES BEING DISPOSED IN SUCCESSIVELY STEPPEDRELATION AND THE COOPERATIVE MEMBERS BEING MOUNTED ON AN INCLINED AXISSO AS TO CONVEY THE TUBULAR ELEMENTS IN SLIGHTLY INCLINED RELATIONSHIP,AND SAID PROTECTIVE ENCLOSURE MEANS INCLUDING A DEPENDING SEALING WALLPROJECTING INTO THE FIRST TANK MEANS BELOW THE LEVEL OF ITS CONTENTS OFTHE FIRST SPACED RELATION TO ONE END WALL THEREOF SO THAT UPON ENTRY OFTHE TUBULAR ELEMENTS INTO THE CONTANTS OF THE FIRST TANK MEANS BETWEENSUCH ONE END WALL AND THE SEALING WALL THE AIR IS PURGED FROM THETUBULAR ELEMENTS AND UPON EXIT FROM SAID FIRST TANK MEANS THE TUBULARELEMENTS FILL WITH PROTECTIVE ATMOSPHERE FOR PASSAGE INTO THE SECONDTANK MEANS.